The trend in many modem buildings is to use large window panels. The architectural desires lead to facades that require screens against sunlight. Most commonly conventional laminar blinds are used to provide the required shading. The size of the slats of such blinds and the maximum free span between the support cords are, however, limited. Simply scaling up the blinds and slats would lead to various kinds of stability problems. Typically in venetian blinds presently available the slats have dimensions up to about 10-cm width and a free span between the support cords of about one meter. The limited span between the support cords and the consequent high number of support cords combined with a large number of narrow slats may spoil the original aesthetic effect provided by the large glass panels. Another solution has been to limit the size of the glass panels to the dimensions of the available blinds, thus limiting the architectural freedom.
Furthermore large, unbroken window panels may lead to acoustical problems in the room bounded by these panels due to undesirable sound reflections from these panels. It would hence be desirable to have access to venetian blinds with extended length of the slats and corresponding extended span between support cords, which venetian blinds could also, for instance as an option, provide desired acoustical damping of reflections from panels covered by the venetian blinds.
Furthermore, the removal of slats for instance for replacement of these can in many prior art venetian blinds be a cumbersome process, for instance due to the lift cords being passed through passages in the individual slats and the slats being supported by the tilt cords according to the traditional ladder-cord arrangement. Such arrangements make the removal and replacement of individual slats difficult and often even impossible without dismantling major portions of the venetian blind. It would hence be desirable to provide venetian blinds of the above kind shaped and attached to tilt cords in a manner that would facilitate removal of individual slats. Furthermore, the provision of passages in the slats—either in the form of centrally located elongated slits as is often done for passage of the lift cords—or along the edge portions of the slats, for passage of attachment means for the tilt cords through each individual slat, is not optimal from a production point of view or from the point of view of cleaning of the slats. Moreover, it makes it difficult to prevent light from penetrating the slats through these passages and for instance the centrally located passages for the lift cord must necessarily be of a relative large lateral extension if the slats have to be able to undergo tilting over a major portion of the vertical tilt range from one of the slats' substantially vertical position through the horizontal position to the other substantially vertical position of the slats.
Slats for venetian blinds where the tilt cords are attached to the longitudinal edge portions of the individual slats are for instance described in GB 1 512 274 and DE 38 19 920 A1.
Thus, GB 1 512 274 discloses slats for a venetian blind comprising longitudinally extending rounded flanges through which staples are driven and secured. Supporting strings are attached to these staples outside each longitudinal edge portion of the slats. This document furthermore discloses a special tool used to facilitate driving the staples through the flanges.
DE 38 19 920 A1 discloses slats for a venetian blind where the longitudinal edge portions are formed as rounded flanges somewhat similar to those of the above document. At the appropriate locations along the longitudinal direction of the slats these flanges are provided with slots cut through the flanges and some distance into the main portion of the slat. Into these slots are inserted clips formed for pivotally engagement with corresponding spherical members attached to the supporting cords.